Photo-electric tube



8- 29, 1933- E. D. WILSON Y 1,924,299

PHOTO ELECTRIC TUBE Filed Feb. 20, 1929 INVENTOR Ear/ B lI/l/sofl.

A"TTORNEY Patented Aug. 29. 193 3 [UN TED{ TAT PATENT 1 onion ."aPHOTO-ELECT ItIC TUBE Earl D. 'Wilson Wilkinsburg, rm; assignor to Westinghouse Electric & Manufacturing Coin.-

pany, a- Corporation of Pennsylvania Application February 20, 1929. Serial No. 341,344 '8 Claims. (01.. 2 215)? This invention relates to photo-electric tubes and particularly to photo-electric tubes'in which a shield-is'provided between the anode and the cathode.

As indicated in the copending application of Allen A. Shoup, Serial No. 340,314 filed Feb. 15, 1929, it is desirable, when a high-frequency carrier current is to be used with a photo-electric tube, to provide a shield in order that the electrostatic capacity between the anode and the cathodewill not convey a current to the amplifier with which the photo electric tube is used. a V I It is an object of this invention to provide such an arrangement of the elements of the photoelectric tube that the shielding means will not interfere with the illumination of the photo-sensitive surface. i

It is a further object of range the elements of the photo-electric tube and their supports in such a way that the cell is convenient to manufacture and the shielding will be effective. i I I It is a further object of this invention'to provide complete and effective shielding between the cathode and both the anode and the conductor.

leading thereto. I

Other objects of the invention and details of the. construction will be apparent from thefol lowing description and the accompanying drawing in which:

Figure 1 is an axial section, and Fig. 2 is a transverse section. V

The photo-electric tube comprises a glass envelope 1 provided at each end with a press 2 and 3, respectively. 'At the end having the press :2, which, as illustrated, is the upper end, the photo-electric tube is supplied with any suitable base 4 equipped with pins 5 to cooperate with a standard socket. A conductor 6 extends through the press 2 andestablishes connection between one of the pins 5 and the cathode 7. 1

l The cathode is in theform of a sheet of material, preferably, flat except'that a margin8 thereof is at an angle to" the main body of the cathode. The sheet is supported upon the standard' 6 and a supplementary standard 9 mounted in the press 2. If an unusually large photo-tube is built, additional standards may be provided for the purpose of supporting the cathode and preventing excessive vibration.

An anode 11 is mounted in the press 3. Preferably this has the form of a straight wire or rod of small diameter. The rod extends through'the press 3 and is conductively connected with a wire 12 extending to the outside of the tube. The

this invention to artop of the press 3 is furnished with a cylindrical glass boss 13 surrounding the foot of the anode.

A'helix 15 of fine wire of relatively large pitchis mounted to surround the anode 11. Any convenient means fol-holding the helix in place may 50 be employed, but I prefer a rod 16, soldered, welded or otherwise rendered metallically in,- tegral with each whorl of the helix. A conductor 17 extends through the press 3 and is con nected metallically with the standard 16 as shown at 18. r This connection is preferable by welding, but any metallically continuous and mechanical- 1y strong connection will suflice.

A disk 21 is supported upon the end of the conductor 1'7. The portion of the conductor}? between the press and the diskis oblique in order to better support the disk, and the lower end of the-standard 16 is at an angle to the remainder thereof in order to make a convenient joint with the bent end of the conductor 17. I

Ametallic cap 22, secured to the disk 21, encloses 'a volatilizable pellet. Supported at the top of the standard 16; is a disk 23 0f approximately the same diameter as theheli'x 15.

A metallic sleeve 25, preferably nickel, of the same diameter as the. helix-15,. surr'ounds the boss 13 and is located in alignment with the helix. The disk 21 has a central opening of sufiicient size to accommodate the sleeve 25 and the standard 16. I r V A metallic sleeve 251 outside'the photo-tube ex tends fromthe end of the photo-tube slightly past the; disk 21, and servesas an external electrostatic shield. I b .ln the-operation of the device, the photo-tube is soplaced that the light enters. through the transparent wall of the envelopeat such an angle to the planeof the main portionof the cathode that the shadow of the anode 1'1 and helix ,15 does not fall upon this part of the cathode." The light thus received upon'the main part of the. cathode is reflected and most of the reflected light may be intercepted by the marginal portion 8 r of the cathode. In this way,fsubstantia1ly the same extent 'of cathode surface is subjected to the light as if the anode 11 and the helix 15 were not present to obstruct. thelight and the light were received normal to'th'e main cathodesurface.

The light is ordinarily supplied to the cathode by focusing upon the cathode an image of an v illuminated slit. With the light received at an acute angle as just described, the image of the slit is wider because the cathode surface is oblique to the light beam. .With the best adjustment,

of silver upon a copper base.

. a way familiar to those skilled in the art and.

need not be described herein.

anode 11 and the cathode '7. It is undesirable that the capacity elfect between thesetwo elements should convey current through the phototube, and the helix 15 with its associated parts constitutes a shield for preventing such capacity The helix l5 surrounds the anode and extends beyond the upper end thereof. At this end the envelopment of the anode iscompleted by the disk or cap 23 which closes the shield at this point.

At the lowerend'of the anode, the completion of the shielding is effected by the metal sleeve 21, which completely fills the cross section of the phototube except for a very small clearance at the inside of the glasswall and a small clearance about the sleeve 13. I Am lines of force from the cathode which extend to the outside of the phototube are prevented from reentering and arriving either at 40' the anode 11 or at the conductor 12, associated therewith by the metallic sleeve 24 which surrounds the disk 21 and extends so far beyond the end of the photo tube that negligibly few lines of force from the cathode reach the lower endof the sleeve.

In the preparation of the photo tube an alterhating electro-ma'gneticfield parallel to the axis of the anode is applied, with the result that eddy currents are set up in the disk 21 and 'the disk is heated. The cap 22, containing the volatizable pellet is heated to such a temperature that the pellet disintegrates and photo-electric material therefrom is released to be deposited upon the cathode.

Many variations of the structuredescribed herein will occur to'those skilled in the art. The

a distance from said portion, whereby,when light I is received at a sufficiently oblique angle to said flat portion, the shadow of said other electrodes will not fall thereon, said cathode also comprising a portion at such an angle to said firstnamed portion that most of thelight received at said oblique angle and reflected by said firstnamed portion will be intercepted by said secend-named portion. I

2. A photo-electrictube comprising an evacuated envelope having two presses, one at each end thereof, a cathode of sheet material sup- I ported from one of said presses, a support there- In use, the phototube may be connected into a circuit by means of which an alternating difference of potential is established between the for including a conductor extending through the press to the exterior of the envelope and an anode and a shield separately supported from the other press by means of supporting members, said supporting memberseach including a conductor extending through said last-named press to the exterior of the envelope. I

I 3. A photo-electric tube comprising an evacuated envelope having two presses, one at'each end*thereof, a cathode of sheet material supported from one of said presses, a support therefor including a conductor extending through the press-to the exterior of the envelope, an anode and a shield separately supported from the other press by means of supporting members, said supporting members each including a conductor extending through said last-named press to the exterior of the envelope and a metal sleeve on the exterior of the envelope cooperating with said shield to complete the electrostatic separation of j the anode from the cathode. I 4. A photo-electric tube comprising a cathode, an anode, a helix surrounding said anode, a disc closing one end of said helix and means at the other end thereof for completing the shielding of the anode;

' 5. A photo-electric tube comprising a cathode,

a press, an anode mounted in said press, a helix surrounding said anode, a metallic sleeve mounted on said press in alignment with said helix and extending from'the helix beyond the en-.

trance of the anode into the press.

6. A photo-electrictube comprising a3press, an anode mounted in said press, a helix surrounding said anode, a metallic sleeve mounted on said press in alignment with said helix and extending from the helix beyond. the point of entrance of the anode into the press, adisk surrounding said sleeve and a sleeve outside the photocell extending from the plane of said disk to beyond said press. I

7. A photo-electric tube comprising a cathode, anv anode, a helix surrounding the anode, a disk concentric with said helix and conductively connected thereto. I I

8. A cylindrical photo-tube comprising an en-, velope, an anode mounted at one end thereof, a cathode mounted at the opposite end and a metallic sleeve surrounding the tube'at the anode end and extending beyond the point of entrance of the anode into said envelope. I I

EARL DQWILsON. 

